Celestial Pearl Danio” Is a Miniature Danio (S.S) (Ostariophysi: Cyprin- Idae): Evidence from Morphology and Molecules

The “Celestial Pearl danio” is a miniature Danio (s.s) (Ostariophysi: Cyprin- idae): evidence from morphology and molecules

KEVIN W. CONWAY, WEI-JEN CHEN & RICHARD L. MAYDEN Department of Biology, Saint Louis University, 3507 Laclede Ave, St. Louis, MO 63103, USA. E-mail: [email protected]

Abstract

The osteology of the miniature cyprinid Celestichthys margaritatus Roberts, type species of Celestichthys Roberts, is described in detail and briefly compared with that of other members of the Rasborinae (notably Danio (s.s), Danionella, Devario, Esomus, Microrasbora, Paedocypris and Sundadanio). Celestichthys margaritatus possesses an “A” stripe on the anal fin and two pigment stripes on the caudal fin (apomorphic features of Danio sensu Fang, 2003). In addition, C. margaritatus exhibits a median projection on the outer arm of the os suspensorium, a derived feature, present only in species of Danio (including D. erythromicron) amongst the Cyprinidae, and a lateral projection on the lateral face of the dentary (present only in Danio, Sundadanio and Paedocypris). Phylogenetic analysis of 1,494 bp of the RAG1 nuclear gene for 31 rasborine taxa, including 5 species of Danio, places C. margaritatus as the sister group to D. erythromicron, and part of a larger monophyletic group including all other species of Danio included for analysis. Based on characters of morphology and its position in a molecular phylogeny of the Rasborinae it is proposed that Celestichthys be placed in the synonymy of Danio, its only member referred to as Danio margaritatus new combination.

Key words: Cypriniformes; Celestichthys; Danio; osteology; phylogeny; RAG1; miniaturization; taxonomy

Introduction

Roberts (2007) recently described Celestichthys margaritatus as a new genus and new species of miniature cyprinid fish from Myanmar. This description was greatly anticipated by the aquarist community, to which this species was known under the common name of “Galaxy microrasbora” or “Galaxy rasbora” (Clarke, 2006a,b). These common names, in reference to the spectacular colour pattern of this species (Fig. 1A), are rather confusing as they suggested that the species was a member of either Microrasbora or Rasbora prior to any taxonomic assignment. In its taxonomic description Roberts (2007) inflated the situation by introducing another common name, “Celestial Pearl danio”, in allusion to the small pearly spots along the flanks. Despite the choice of common name, however, Roberts did not place this new species within Danio but instead cre- ated a new generic name, Celestichthys, for the sole inclusion of this miniature species, with slight reference that one other miniature species, Danio erythromicron (Annandale) (refered to as “Microrasbora” erythromicron) might also be a congener. Little is known about the ecology of the “Celestial Pearl danio” other than that it inhabits small and shal- low ponds with adundant aquatic vegetation (Roberts, 2007). Until recently the distribution of C. margaritatus was believed to be resticted to the type locality (ponds at the foot of a mountain near Hopong Town, 30km east of Taunggyi, Myanmar; Roberts, 2007). However, it is now known to have a much wider distribution within Myanmar (Clarke, 2007) and has even been reported from Thailand (Hary, 2007). Roberts (2007) diagnosed the genus Celestichthys and its species, C. margaritatus, from all previously known Asian Cyprinidae by its distinctive head and body shape, small upturned mouth with shortened jaws,

Accepted by A. Gill: 28 Nov. 2007; published: 21 Jan. 2008 1